1. Field of the Invention
The present invention relates to a joint structure for a branch connector by a branch pipe or a branch fitting in a common rail such as a high-pressure fuel manifold or a block rail in a Diesel internal combustion engine.
2. Description of the Prior Art
In one of this kind of joint structure for a branch connector of the prior art, as shown in FIG. 7, a through hole 11-2 formed in the circumferential wall of a main pipe rail 11 and communicating with an internal conduit 11-1 is formed to have a pressure receiving seat 11-3 opened to the outside, and a ring-shaped joint fitting 13 enclosing the outer circumference of the main pipe rail 11 in the vicinity of the pressure receiving seat is used to bring a pressure seat 12-3, which is formed by a joint head 12-2 of a branch connector 12 tapered by the buckling method, into abutting engagement with the end portion of the pressure receiving seat 11-3, so that the branch pipe 12 is jointed to the main pipe rail 11 by fastening a male nut 14, which is assembled in advance in the branch connector 12, by the pressure below the neck of the joint head 12 into a threaded wall 13-1 protruded from the joint fitting. Here, reference numeral 15 designates a sleeve washer.
In this joint structure of the prior, however, the product weight at the connected portion is seriously increased by the use of the aforementioned ring-shaped joint fitting 13 thereby to raise a difficulty that the product weight cannot be reduced. Since the joint fitting is merely fitted on the main pipe rail 11, moreover, its positioning takes a long time, and the joint fitting may be brought out of position in the axial direction by vibrations or impacts. This out-of position invites a slackness to induce a leakage thereby to make the connection unstable. When the branch connector 12 is removed, moreover, another problem may arise in that the joint fitting 13 may move in the axial direction to allow the dust to steal from the outer surface of the main pipe rail 11 into the clearance between the main pipe rail 11 and the joint fitting 13.